Process for reducing the oil absorption of titanium dioxide pigment



Patented Nov. 1, 1932 2 GABRIEL RUBIN, 0F AUBSIG, CZEOHOSLOVAKIA, ASSIGNOR, BY'IEBNE ASSIGNMENTS,

'10 KREBS PIGHENT AND COLOR GOBPOBA'I'ION, OII' NEWARK,

CORPORATION OF DELAWARE new many, A

PROCESS FOR REDUCING THE OIL ABSOBP'IION O l TITANIUI DIQXIDE PIGIEN'I! Ho Drawing.

vMy invention relates to an improved titanium dioxide pigment characterized by a low oil absorbing quality and also relates to a process for producing such a pigment.

Methods for producing white titanium dioxide pigments by hydrolytic precipitation from titanium salt solutions are well lmown in the artend have been described by Blumenfeld in Patent No. 1,504,672 and in the following copending appiications by Blumenfeld: Serial No. 128,322, filed August 9, 1926; Serisi No. 128,324, filed August 9,1926; Seriei No. 251,253, filed February .2, 1928; and Serial No. 258,141, filed February 29, 1928 After the bydrolytic precipitution of titenium dioxide from the salt solution, the

preeipitete is filtered, washed end calcined at 900 to 1,@d in s manner Well known in the Subsequent to the cslcmetion, it is necessary to bieei: up tlie aggregetes by e-grinding process. To achieve :1 .useiui result this grinding must be done while the titenlum dioxide is not. For the reason mentioned it is the custom in the art to piece the calcined product in e boil miil in the presence oi waiter and to grind the some for some hours to secure ofine state of division of the pigment,

, the average perticle size being in the neighborbood of ,5 s. The wet-ground pigment is then dried in the usual manner,

Titeniuni dioxide pigments produced by the processes descriMd ere valuable in the point making art on account of their high hiding power end tinctoriei strength. The

- rately weighed and placed in a clean glass plate; About ten drops of refined linseed oil are added at one time from a, graduated burette and the oil is lightly worked into the Application filed February 16, 1829. Serial No. 840,652.

in which tile ooted to cons1 erable pressure or momenteuy pigment with a spatula. "The addition of oil is continued until the pigmentis thoroughl wetted and the whole mass is lastic. t the end point, the addition of one extra drop of oil will cause the pigment to smear on the plate. o

I have now discovered that the oil absorption number of a titanium dioxide pigment may be greatly reduced and the other pigmentery qualities likewise improved by a surprisingly simple process and that a new and more valuable pigment may thereby be obtained. This process cons'mts in grinding the pigment in dry condition. By the term grlnding, as used in the specification and claims I refer to a ulverizing process articles oi pigment ere sublmpact. I have discovered that titunium' diomde pigment produced by the usuci" Wet grinding process and buying on oil absorption varying from 35 to mey be trons formed into a pigment having oii absorp tion of 25 or less by dry-grinding.

This process many be curried out in the laboratory on a smell scsle,-by Vigorousiy grinding a few grams of titanium dioxide pigment.

in a mortar. The same efiect may beobteined on on industrielscele by grinding the titanium dioxide'pigment in [e dry condition in Raymond mill or a chocolate mili. Tue time required for such a process Wiii naturally do pend on the size of the miii end the emount of pigment pieced in it but i have found that in normal plant operation in gninding period of one or two hours will sufiice The quantitative reduction of the oil ebsorption number, achieved by the improved process, depends on the oil absorption number prior to treatment, The higher the initial number, the greater wili be the pi opon tionete reduction. The process also has the effect of improving the hiding power of the pigment as determined by the cryptometer, oy about 540%. The process also produces an increase in tinctoriel power in the neighborhood of 20% as determined according to the method of Booge (Point Oil and Chemical Review, May 28, 192 2).

The great reduction in oil absorption pro-- duced in previously wet-ground titanium dioxide pigments by dry grinding these materials in a'laboratory mortar is llustrated in v the following tabulation which shows the effqict of dry grinding various pigment samp es. s

claim -1. A process for reducing the oil absorption of titanium dioxide pigment which comprises regrinding said pigment in a dry condition; p

2. A process for producing titanium dioxide pigmentcharacterized by a low oil absorption which comprises wet grinding calcined TiO,, drying the same, and grinding said pigment in dry condition.

3. A process for producing titanium dian oxide pigment characterized by a low oil ab 7 sorption which comprises calcining TiO, re duced b h drolytic recipitation, wet grind- I ing sai ca cined Ti drying the same, and

grinding said pigment in dry condition. as 4. A process for producing a titanium dioxide pigment of low oil absor tion which comprises wet grinding calcin ,TiO, drying the same, and grinding said heated pigment in dry condition until its oil absorption has been reduced at least 25%. M '5. A process for producing a titanium dioxidev pigment of low oil 'absor tion which comprises wet grinding calcin TiO drying the same, and grindin said pigment m dry condition until the 011 absorption has been reduced to an oil absorption number of at least 25. I v 6. A procem for produc' a titanium dioxide pigment of low oil a rption which compr ses wet grinding'calcined TiO,, drying the sameiand submitting said'pigment in the dry state to a ulverizing process in which the particles 0 the pigment are subiected to considerable pressure. a In testimony whereof, I have signed my 7 name to this specification this 25th day of January, 1929.- Y V GABRIEL KUBIN.

Now haying'desq-ibed my invention, I 

